1. Field of the Invention
The present invention relates to a frame structure of a vehicle seat for absorbing an impact generated upon a rear-end collision by bending of a seat frame.
2. Description of the Related Art
A vehicle seat includes a seat-cushion, a seat-back and a reclining system. The reclining system connects the seat-back to the seat-cushion so as to be capable of moving between an upright position and a reclined position.
When the vehicle encounters the rear-end collision, an occupant seated on the vehicle seat is pressed toward the rear of the seat due to the impact thereof. The seat-back is positioned upright at a predetermined angle of inclination with the reclining system. The occupant must be supported by the seat-back. In order to do so, a configuration (frame structure) which causes another frame component to bend to absorb the impact of the rear-end collision is necessary to protect the reclining system.
A kind of a frame structure is described in JP-A-2001-178584. This structure includes a reclining system and a bracket. A cushion frame and a back frame are connected via the reclining system. The back frame is mounted on the reclining system via the bracket. The bracket includes a main plate shaped as a flat plate and a flange to be connected to the main plate. The flange has a substantially L-shape (side cross-sectional view).
The bracket includes a bead. The bead is a portion that is formed by depressing an outer wall of the bracket inwardly of the bracket in a triangle shape. The bead is formed on the bracket so as to extend across a borderline between the main plate and the flange.
The impact of the rear-end collision of the vehicle is absorbed by bending of the bracket (outer wall) starting from the bead. The impact which is transmitted to the reclining system is alleviated by the impact absorption as described above.
However, this frame structure does not include configurations to absorb impact other than bending of the bracket (part of the back frame) by plastic deformation. Therefore, sufficient alleviation of the impact of the rear-end collision is not achieved by the frame structure.
The vehicle seat is adapted to transmit the impact of the rear-end collision to the cushion frame which is joined to the back frame. Therefore, the impact of the rear-end collision can be sufficiently absorbed by bending the cushion frame. However, since the occupant is seated on the cushion frame, the cushion frame should not be bent in an arbitrary direction.